Dipper's 18th Birthday Surprise
by The Angry American
Summary: Dipper Pines has finally turned 18, the age of adulthood. But on one special night, what'll happen when a certain red-head gives Dipper a surprise present that he'll really remember? TWO-SHOT. Warning: Features Mature Content and sex. Not for the fate of heart.
1. Chapter 1

**Dipper's 18th Birthday Surprise  
**

**Rated T (soon to be M)  
**

**Disclaimer: I definitely do not own Gravity Falls. Gravity Falls is owned by Disney and Alex Hirsch  
**

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**Chapter 1**

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18. Nevertheless, it was the age to be.

For Dipper Pines, having to be 18 was a priority. Which meant that he wasn't gonna take orders from his Gruncle Stan. It also meant that he could finally live free on his own occasions without having to be nuttily freaked out by his twin sister Mabel.

The main reason for Dipper is... being 18 meant that he was stepping out from childhood to adulthood.

But he was a long way from being 18 just yet. Now that Mabel's first part of the birthday was finished, it was about time for Dipper's part.

Strangely, Dipper was out of town to get some tree sap that Gruncle Stan needed. After all, how would Gruncle Stan's pancakes be like without any maple syrup? It would be like french fries without any amount of ketchup.

Outside on perhaps what was a hot summer day, Dipper was struggling to get the huge jar of tree sap inside the house.

"Oh, man... this really sucks. Gruncle Stan should've asked Mabel to get the tree sap, but no... he had to go ahead and choose me." Dipper grunted, "Once I'm 18, I'll finally get out of the Mystery Shack with no one telling Dipper what to do."

Using his last ounce of strength, Dipper managed to barge in the door and fell to the floor, alongside a jar of tree sap. Luckily, the jug was unbroken and the cork was plugged in tight. When Dipper got up and picked up the jar, he looked at what came to him:**  
**

_"SURPRIIIIIIIIIIIIIIISE!"_

"AAAAAAAGH!" Dipper screamed.

The image he saw was his twin sister Mabel and her faithful companion Waddles, his greedy Gruncle Stan, his best buddy Soos, Mabel's friends Grenda and Candy, his crush Wendy, and to no surprise, Dipper's arch-enemy Robbie. Of course, Robbie would be caught dead coming here to such a childish 18th birthday party. But since this was Wendy's treat, Robbie had no choice but to come.

Everyone all around Dipper had changed. Mabel finally got her braces out, Waddles got a bit bigger, Gruncle Stan was still the same old bag, Soos lost a little weight, Grenda and Candy still looked like themselves but a bit taller, and Robbie was now less of a punk. His behavior and harsh feelings for Dipper sorta cooled off for good.

But something was missing. What was it that Dipper forgot?

Oh yeah... Wendy. Dipper couldn't forget about her. The girl who haunts Dipper's dreams all day and night. He couldn't even sleep a good nano-second without ever thinking of that beautiful red-head. Years had passed and she still looked the same as ever. Sure she looked a little taller, but nevertheless, she still remained the same old Wendy.

Dipper got back to his feet after being surprised.

"Wow! You really scared the heck outta me..." Dipper said with his heart palpitating.

"Happy birthday, little brother!" Mabel shouted out happily before she blew the party snake right across Dipper's face.

"You know, you didn't have to do that, Mabel..." Dipper blushed at Mabel, noticing that Wendy was here.

"C'Mon, I'm your sister! This is your party!" Mabel happily exclaimed while he hugged him tightly.

"Mabel's right, Dip..." Gruncle Stan spoke out to him, "You're growing up into an adult now. Your parents must be proud of you and your sister turning 14 years old."

"Um, Gruncle Stan? I'm 18 years old." corrected Dipper.

"Like it matters, kid. Anyway, enjoy your presents and your cake." Gruncle Stan said while he went to the kitchen, "And if every one of you even thinks of getting your cake morsels anywhere near the floor or my favorite chair, I ain't cleaning it up!"

Following Gruncle Stan's threatening reminder, both Grenda and Candy began rolling in the tasty birthday cake that they made for Dipper. It looked a little screwed up considering that they didn't attempt to make the cake look like Dipper's entire face. Dipper's eyes was made out of olives while the rest of the frosting had a very fishy smell. It was perhaps the worst cake that Dipper had ever seen. The only good thing about this cake was it had candles. All 18 of them.

"Okay, bro. You got your own cake. It's tasty, delicious, and it gives out that nice seafood smell!" Soos said while he placed his hand on Dipper's shoulder.

However, the mist of that strong fishy smell made Dipper cringe from the inside.

"Um, Soos... no offense, but this cake smells like Gruncle Stan's crusty underwear...", criticized Dipper.

"How did you guess the flavor? I must be a genius!" Soos admiringly said to himself.

"Yeah... you really are..." Dipper said, feeling an edge of shame inside.

"C'mon, dork. Make a wish already!" Wendy exclaimed, while she wrapped his arm around Robbie like a bro would ever do.

"Okay, then..." Dipper replied. His face went near the birthday candles and closed his eyes. It was then that his thoughts began to make that one single wish for him.

_"I wish I could have Wendy all to myself..."_

After he reopened his eyes back up, Dipper took a deep breath and blew out all 18 candles. It was nice to say that those candles had a strawberry scent. At least it made up for that horrible fish smell that the cake had. Basically, Mabel and her friends were horrible cake makers.

All Dipper cared about was the presents that he had. Even though it was pretty much a rough economy, Dipper was fine with the gifts he got.

Soos got him a new black trucker hat that said "All The Ladies Love Me".

Mabel, Grenda and Candy made him a bracelet that said, "Dipper, Best Brother In The Werld". Sure, Mabel screwed up the spelling, but that statement was definitely enough.

Although Robbie wasn't a gift giving type of guy, he did give Dipper the best thing money could ever buy. He gave him a CD of his band. He also told Dipper that it was some of his best work.

Gruncle Stan on the other hand, would have given Dipper nothing since he was nothing more of a greedy man. But since it was Dipper's birthday, he decided to give him $100 dollars. It was like one Benjamin Franklin wrapped in green.

The only person that forgot to give Dipper a present was Wendy. To make up for forgetting his present, Wendy gave a Dipper a note that read something like this.

_**Dipper**_

_**Meet me in the secret room inside the Mystery Shack all alone at midnight. It's all about your present that I forgot.  
**_

_**Don't forget, Wendy**_

Such a weird present. How could Dipper not get a present for Wendy? This was outrageous. He yearned to find out from her one way or another.

It was 30 minutes way before midnight as Dipper started flipping his new hat around. Everyone had already turned in for the night, including Waddles, who had such a bellyache from eating Mabel's fish cake. Mabel, who was already in bed, turned to Dipper.

"Hey, little brother... have you thought what Wendy got you?" said the braceface.

"I got no idea, Mabel. Maybe it's a console version of Fight Fighters. I've been dying to play that game on the GameBox 540!" Dipper said in a very calm, yet anticipated tone.

"I hardly think Wendy got you that." Mabel spoke back.

"I think so? Maybe it's those tickets to see that rock band in Portland. After all, it's only a few miles away from Gravity Falls."

"Doubt it." Mabel chuckled, "If Wendy were the only woman who can score tickets to a hip show, chances are that she'll take Robbie instead of you."

"Very funny, Mabel." Dipper snarled back, "I hardly think Wendy would would do that."

"Are you sure...?" Mabel said in a sing-songy way.

"Yes, Mabel. I'm sure of that."

The clock was now ticking consciously. Dipper's patience grew very thin. His teeth was gripping from his own gums and an ounce of sweat was dropping from his head. Dipper was about one second away from blowing up with intense power.

Annoyed by the tick-tocking noise, Dipper stood up out of the bed.

"Okay, I sooooo cannot take this anymore! I gotta go to Wendy right now."

"Good luck, then. You'll need it." Mabel winked while she went back to sleep.

"Well, unlike your chances with a guy, I won't need luck." Dipper said while he was about to leave. But before he could leave however, he turned to his sis, "Wait, why on earth do I need luck for?"

Dipper never got an answer from Mabel. All he heard was her snoring. Safe to say, Dipper was annoyed by her response.

"Sometimes, I regret having a nutjob as my sister..." Dipper said to himself while he walked out of his room quietly.

What was he gonna expect from Wendy? Whatever this was, it was gonna be a night that Dipper would remember.

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**Can many of you guess what'll happen in the next chapter? I wish I told ya, but you'll have to find out. I trust ya, this is something you'll never want to forget. Until then, R&R!**


	2. Chapter 2

**Dipper's 18th Birthday Surprise  
**

**Rated M for Sex and Language  
**

**Disclaimer: I definitely do not own Gravity Falls. Gravity Falls is owned by Disney and Alex Hirsch. Here comes the best part of my little two-shot. So for those of you who have a weak stomach, don't read. If you choose to read... well... good luck! (;D)  
**

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**Chapter 2**

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_Thump-thump... thump-thump..._

That was the only sound that Dipper was hearing. He was feeling a bit tense about this situation. The thoughts of Wendy and himself alone in the secret room made his heartbeats pound loudly in nervousness. It was close to giving out on him permanently.

"Okay, Dipper... you can do this..." Dipper said to himself as he approached the door.

With a deep breath, he decided to reach for the doorknob. But Dipper quickly turned away, thinking such second thoughts.

"Okay, I can't do this..."

Dipper began to walk away quickly from the door, but soon stopped. He looked right at that door once again.

His body shook uncontrollably. His tongue bit with nervousness. And so far, Dipper's forehead began to sweat. Why on earth was he walking away for? That note that he had from Wendy was important. He wasn't gonna blow it all on this one night. After all, he wanted to finally get some alone time with Wendy.

Which meant no Mabel, no Gruncle Stan, no Soos, no Waddles, and definitely no Robbie to interrupt quality time. It was then that Dipper finally turned around and approached the doorknob once more.

"All right... here I go."

With another deep breath, Dipper opened up the door.

But to his disappointment...

...

...nobody was there. It was nothing but cold, empty darkness with the moon as the main source of light.

"I don't understand... Wendy told me to wait for me here at midnight, but somehow it's 12:05..." Dipper said with a stunned expression, "I hate to realize that I'm being played here..."

But before Dipper could even think about leaving, he noticed an another note laying down on the comfy sofa.

Curious, he picked it up and read the contents. From the contents of the note, he read:

_**Dipper**_

_**Look to your right. That is all.**_

_**Love, Wendy**_

When Dipper did what the note told him to do, his world was stopped by two words:

"Hey, Dipper..."

Dipper couldn't believe his eyes for a minute. What he was looking at just happened to be Wendy. But something was different about her in anyway.

She was dressed in a silky white see-through nightie with a lacy white bra and panties. Dipper was speechless and stunned. Stunned because he never saw Wendy look damn good as of right now. And speechless because of the way that Wendy's bust size had suddenly increased. She went from a b-cup to a c-cup in just a short amount of time.

Dipper didn't know how to react. He was stuttered speechless.

"W-W-Wendy?"

"Why so scared, Dipper?" Wendy seductively chuckled, "I thought you'd be happy to see me."

"Well, yeah..." Dipper blushed while rubbing the back of his neck, "But seeing you like this... it's a bit awkward."

"Awkward? Dude, you don't have to sound so gay." Wendy chuckled, "This is your birthday. Live it up, dork."

"Yeah, about that... I kinda noticed that you didn't get me a present..." Dipper said with a hint of disappointment, "Any reason with that?"

"Dude, about the present. There's something I gotta confess..."

Her tone of voice turned very sultry and very exotic as Wendy turned to the door and locked it. Dipper felt a bit nervous, but why shouldn't he be? This was Wendy he was looking at... and in lingerie! Dipper should be excited on both the outside and the inside, but he decided to play the nervous act just for fun.

After she locked the door, Dipper got cornered in a wall, noticing that Wendy was strutting slowly towards him. Micro-seconds later, Wendy's body was pressed into Dipper's as she whispered into him.

"I'm your present, Dipper. Happy birthday..."

Dipper was about to speak, but he didn't get the chance to.

Instead, he was cut off by a passionate kiss from Wendy. Feeling his lips pressed, Dipper's eyes popped up like an air bag! Maybe it was from her slippery tongue that caused the pressure in his eyes to inflate. Dipper wanted to fight back, but he couldn't. Luckily, Dipper didn't want to fight back.

His response to the kiss was magical. He returned with a kiss of his own, just to outmatch Wendy's tongue with his. The match was very intense from the start. His tongue moves emitted a very passionate moan from Wendy, which made music to Dipper's ears like none other.

The makeout forced Dipper's hands to grab a hold of the strap from Wendy's see-through white lingerie. He sent the piece of silk sliding down off her shoulders and onto the floor. Dipper then proceeded to hook Wendy's white bra off her body. With flying colors, Dipper finally got the thing off.

After breaking off that kiss, Dipper marveled at the bare cleavage that was Wendy. Her pale white breasts were the most extravagant thing Dipper saw coming from his now 18-year old mind. It was so luscious and tantalizing that Dipper wanted to get a handful, but he couldn't.

"Mmmmmm... I never knew you were an excellent kisser..." Wendy smiled.

"Well, I used to kiss Skittles taped to a bathroom mirror..." Dipper chuckled nervously.

"Nice little life story..." Wendy nodded, "Let's see what Dipper's got hiding in his shorts now..."

Contrary to Wendy's words, her hands got a grasp on Dipper's zipper (that rhymed), and sent the little silver jewel sliding off his shorts. When Wendy looked back up, she was really amazed at the sight. All eight inches of Dipper's prime meat. Who knew that an 18-year old with such a skinny build had such a strong manhood?

Licking her pale yet sweet lips, Wendy charged and sent Dipper's entire size inside her mouth. Pushing in and out, Wendy's lips felt the stiff pink rim ram her slowly through her throat. It was gonna be sore, but this is what Dipper wanted for his special occasion. She wanted to taste him, stroke him and suck him every chance she could get from all of this.

"Oh, Wendy... Ohh! Ohhhhhhh..." Dipper moaned heavily while biting his tongue. His little 8-inch friend was being washed down, watered down and polished back and forth. It was like a car being washed, only if the car became Dipper's hardened erection and the entire foam being Wendy's entire stream of saliva.

Wendy's head started pushed harder into the muscle which forced more moans coming from Mabel's twin brother. In her point of view, Dipper had a bit of a honey taste. It was like taking one taste out of a beehive. Dipper's eyes started to roll from the back of his head, feeling the intense pressure. He gripped to the couch cushions uncontrollably, feeling the amazing sexual turbulence.

Wendy soon separated from Dipper. Not too long ago, Wendy laid on the bed and spread those silky long legs to him. Dipper gleamed an amount of sweat going straight to his forehead. His manhood was begging to give her more.

"Come and get me, birthday boy..." Wendy smiled devilishly to him. Dipper read her seduction like a clear book.

With a devilish smirk, Dipper carefully inserted his erection into Wendy's walls, to the point that he began shifting his hips back and forth. Wendy squealed with delight as she took a good job withstanding the sexual pain from Dipper altogether. His throbbing cock felt an amount of heat and blood flow coming inside her. The sensation containing their combined body heat became highly at best, which meant deeper penetration and harder thrusts.

"Ohhhh, Dipper! DIPPER...!" Wendy moaned in rapturous delight while clinging on to Dipper's flesh. She didn't this pure sexual madness to end. Luckily, Dipper didn't want to stop. His hardened bulge pounded her vaginal section one by one. So far, Dipper was winning the battle.

Dipper was now sweating like holy hell. Being dripped on by his sweat, Wendy found it as a turn-on, which was very interesting since she was always turned off when Robbie sweated. The sweat which dripped down to Dipper's third leg, made perfect lubricant in which Dipper could slide in and out with the perfect amount of speed.

After one huge thrust, Wendy whispered to him those angelic words of hers. The kind of words that Dipper stood still to hear.

"Take me, Dipper. Take me once again..."

"Gladly..." Dipper panted in desperation.

Being turned on by Wendy's pleading, Dipper managed to turn her over in all fours. Carefully, yet gently, Dipper plunged his monstrous erection into Wendy once again. Holding on to her creamy hips, Dipper pressed onto her slowly.

"OHHH!" Wendy moaned and blushed, as she once again felt the sexual madness of Dipper once more. Huffing and puffing, Dipper charged right at her rump repeatedly while his speed started increasing. At first, he went nice and easy, but when seconds passed, his thrusting started getting rough in just a matter of seconds. Wendy always had the perfect ass, noticing that she always wore those tight black jeans.

"I'm just... about... there..." Dipper whispered/moaned to Wendy as his thrusts forced his bulbous muscle to twinge in height. Right at the same time, he felt a bit of dehydration wasting away from him. But Dipper never cared one bit. The only thing he cared about was having Wendy all to himself.

Dipper's rod shook and vibrated an ounce of pre-cum. His sexual momentum was about moments away from blowing up like an gigantic amount of fireworks. His speed intensively creased and his entire body was sweating hard like he was trapped in a dastardly volcano. He wanted to hear Wendy scream out his name all throughout the Mystery Shack. And after one final thrust, Dipper was about to explode with glory.

"OH, GOD! I'M CUMMING! AGGGGGGGGGGGGH!"

With one scream from Wendy, Dipper had successfully planted his seed inside her womb. She felt every ounce of Dipper's seed inject her like a snake injects venom inside a person's skin, killing him/her on impact. Basically, this little escapade would proceed Wendy into pregnancy, but since she was on the pill (thank goodness), Dipper was in a victorious state of bliss.

After that crazed act of pleasure, Wendy collapsed on top of Dipper, who also passed out from excitement as well. His entire body was spent and the entire world around him was spinning. While cuddling with Dipper, Wendy looked up to him with an ounce of innocence._  
_

"This... was... amazing..." Wendy chuckled while her face looked very worn out.

"No kidding... that might have been the best birthday present of my life!" Dipper said with glee.

"Best of all... no one came to interrupt us. That's a bonus." Wendy said once more, feeling an ounce of snuggling coming from Dipper.

"I hear ya. I'm even glad they didn't embarrass me this time..." Dipper said in unison.

While both Dipper and Wendy met each other in a sexual embrace...

...they were cut off by the sound of a party favor!

"AGGGGGGGGH!" Dipper and Wendy screamed. Irritated, Dipper turned to the figure who showed up at the door, "Mabel, what the hell?!"

"Happy first time, Dipper!" Mabel cheered before he turned to the hallway, "Hey, everybody! Dipper just had his first time! And it's with a girl!"

Dipper looked a little red-faced and embarrassed. Was Mabel watching through the door the entire time and yet neither Dipper and Wendy found out about it until now?

His embarrassment continued much further when Gruncle Stan, Soos, and Waddles came up behind Mabel. In surprise, Gruncle Stan presented with a birthday cake that said, "Happy First Time, Dipper". At least it didn't smell like fish and crap. It had more of a strawberry smell. Unfortunately, the only things Dipper were smelling was frustration and pity.

"Guys! A little privacy, here? You're embarrassing me and Wendy!" Dipper shouted out in anger while his greedy Gruncle Stan presented him with the cake.

"Here you go, kid! You went from virgin to full-grown man in one day!" Stan smiled, "And don't even think about having me clean up your sex grease. You're doing it yourself, kid."

Feeling a bit embarrassed by this situation, Dipper placed his hat face first onto his face in shame. I guess the 'embarrassing' part that Dipper brought out happened to be true. Oh, how Dipper regretted it so.

"Note to self: Move out of Mystery Shack and never come back..." Dipper muffled through his hat.

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**Nice way to end this hot little two-shot. I swear, Mabel is like a cute little troll that sneaks up on you. I like it.  
**

**Feedback is greatly appreciated. ^_^**


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